Process for the production of iron powders



Patented June 23, 1942 PROCESS FOR THE PRODUCTION OF IRON POWDERS KarlBauer, Frankfort-on-the-Main, Ge any, assignor, by mesne assignments, toC emical Marketing Company Inc., New York, N. Y.

No Drawing. Application November 19, 1938, Se-

rial No. 241,462. 1937 My invention relates to a process for theproduction of ironpowders.

According to this invention iron powder, which is characterised by itshigh degree of purity and great reactivity, is prepared by electrolysinga ferrous chloride solution, which contains ammonium salts, for exampleammonium chloride, ammonium acetate, or ammonium propionate, in thepresence of such quantities of organic acids that the solution has a pHvalue of 6.5 to 7.2. Formic acid, acetic acid, lactic acid, propionicacid and the like may be employed as organic acids. For many purposesformic acid has proved to be particularly advantageous.

The electrolysis is with advantage carried out with high cathodiccurrent densities, for example current densities of 4 to amperes perdcmF, preferably 6 to 7 amperes per dcmfi, advantageously at elevatedtemperature for example about 50-70 C. V

Plates of wrought iron or ingot iron are with advantage used as anode.In the production of the purest iron powder a starting material ofcorresponding purity is employed, for example one which is free fromsulphur and silicon'and particularly also of impurities which deposit onthe cathode, such as manganese.

Iron plates may likewise be employed as cathode.

The electrolysis is with advantage carried out by causing theelectrolytes to flow through a series of cells. When carrying out theelectrolysis care must be taken to ensure that the pH value remainswithin the limits to be maintained according to the invention. Theelectrolyte has a of the current. The properties of the cathode product,for example with regard to texture and solubility, may be therebychanged to anundesired degree.

The cathodically deposited iron, which, after being scraped off from theelectrode, is preferably thoroughly washed, and with advantage dried invacuo at low temperatures, is practically free from carbon and otherdisturbing impurities. The resulting products depending on the degree ofpurity of the initial materials, contain for example about 98% and moreof metallic iron. Owing to its great hardness the cathode product can becomminuted to any desired degree of fineness, for example in ball millsor edge mills. It is extraordinarily reactive, which is evidenced interalia by the-fact that the. iron powder rapidly dissolves at ordinarytemperatendency to become alkaline owing to the action In GermanyDecember 16,

3 Claims. (Cl. 204-40) ture in dilute acids, for example hydrochloricacid.

It has been further found that by suitably selecting the acid to beadded to the electrolytic solution the reactivity of the iron powder canbe considerably influenced. By adding formic acid, for example, an ironpowder may be obtained, which can be handled both moist and also dry inthe presence of air, but which, when caused to glow at one point by'ignition, continues to smoulder in the air. By adding acetic acid, forexample, an iron powder may be obtained, which on contact with air canbe caused to ignite spontaneously. If desired difierent rganic acids maybe added to the electrolytic bath and thereby combined effects may beobtained. The following examples serve to illustrate how the process ofthis invention may be carried into effect:

1. Such a quantity of formic acid (83-85%) is added to a solutioncontaining 35 gms. of ferrous chloride and 100 gms. of ammonium chlorideper litre, that the solution has a pH value of 6.5 to 7.2. About 2-3gms. of formic acid per litre of electrolyte are required for thispurpose. A wrought iron plate free from disturbing impurities isemployed as anode and an iron plate is likewise employed as cathode. Thesolution is electrolysed at 60 C. with a current density of 6-7 amperesper dcm? and a voltage of about 1 to 3. During electrolysis the pH valueof the electrolyte is if necessary maintained within the region of 6.5to 7.2 by further addition of acid.

. in the presence of air. If it is caused to glow at one point byignition it continues to smoulder in the air.

2. Such a quantity of acetic acid is added to a solution containing 30gms. of ferrous chloride and 120 gms. of ammonium chloride per litrethat the solution has a pH value of 6.5 to 7.2 A wrought iron plate freefrom disturbing impurities is employed as anode and an iron plate islikewise employed as cathode. The solution is electrolysed at C. with acurrent density of 5-6 amperes per dcm. and a voltage of about 2. Duringelectrolysis the pH value of the electrolyte is maintained within theregion of 6 to 7 by the further addition of acid; After 12 hourselectrolysis the deposited iron is thoroughly washed in water, driedunder the exclusion of air and ground. The material ignites in a moistcondition in air.

What I claim is:

2. A process for the production of iron powder of great reactivity,which comprises electrolyzing 1. A process for the production of ironpowder of great reactivity, which comprises electrolyzing a, ferrouschloride solution containing ammonium chloride at a current density of6-7 amperes per dcrn. in the presence of formic acid in such a quantitythat the pH value of the solution lies between 6.5 and 7.2.

